UV unwrap causing texture to warp
Once you have your model done, then do the unwrap. It looks like you are trying to do the unwrap as you go, and the model is not square and level in relation to the vertex positions. If you select all the faces there in the front of the object and in the matching view select 'project from view' then the texture should not warp - but you will need to do this for each side of the model, and you will have to adjust for scale matched to the texture.